The present invention relates to a drying drum for fluid materials such as sugar or leached sugar beet cossettes. The drying drum comprises a horizontally arranged drum jacket which is supported along its length at least at two positions by means of bearing rollers. The drum jacket is driven by drive means which rotate the drum jacket about a rotational axis.
Heretofore, the construction of the driving device for prior art drying drums has caused considerable difficulties. It is conventional to surround the drum jacket with a ring gear and to drive such ring gear by means of a rigidly supported drive pinion. However, this arrangement has several disadvantages because due to the large dimensions of the drum, it is not possible to effectively support the drum in such a manner that a satisfactory circular rotation is accomplished at least of that drum jacket portion to which said ring gear is attached. However, such satisfactory circular rotation is essential for an efficient meshing between the ring gear and the drive pinion.
Furthermore, due to the large dimensions of the ring gear, correspondingly large dimensional deviations occur because the manufacturing tolerances cannot be limited beyond a range which would increase the manufacturing costs in an unreasonable manner.
Still other difficulties are caused by the fact that the drying drum, during its operation, is subject to the weight of the materials being dried and that the drum is simultaneously exposed to high temperatures because a hot gas stream is conducted through the material in the drum. These gases may enter the interior of the drum at a temperature which depends upon the particular drying job and which may reach up to about 1,000.degree. C. Consequently, substantial heat expansions as well as uncontrollable warpings of the drum jacket cannot be avoided. Thus, it happens that the ring gear moves radially as well as axially relative to the rigidly supported drive pinion during the rotation of the drum jacket. As a result, it is not possible to realize an optimum meshing between the ring gear and the drive pinion.
A faulty intermeshing usually results in overloading of the flanks of the gear teeth which in turn causes a heavy wear and tear of the intermeshing teeth which is unavoidable. Even supporting the drive pinions in a yielding manner does not result in any appreciable improvement of the intermeshing between the gear teeth although such yielding support of the drive pinion increases the costs.
It is further known to provide the drum jacket of a drying drum at one end thereof with a shaft which extends coaxially relative to the rotational axis of the drum. However, in this known construction, the shaft constitutes a supporting element because the shaft replaces the second set of bearing rollers which are generally employed in connection with this type of drying drums. It has further been suggested to drive the drying drum through this shaft which constitutes a bearing means for the drum. However, this is not satisfactory because it is unavoidable that the end of the shaft performs a wobbling motion. Therefore, this known construction requires expensive, universal joint couplings for driving the drum through the shaft which couplings are subject to wear and tear.